Reflecting material

ABSTRACT

A material for thermoforming comprises a plastic layer as well as a layer of reflecting pearls in an adhering transparent substance. The material is suitable for the manufacturing of a reflecting product by means by vacuum forming.

[0001] The present invention refers to a material for thermoforming aswell as to the use of this material for the manufacturing of areflecting product by means of thermoforming.

[0002] While performing different activities during more or less badlighting, it is important for a person performing the activities to becompletely visible. At present, a person can obtain a lower degree ofprotection by different types of reflex tapes, so as to be visibleduring poor light conditions. This does not only apply to differenttypes of spare time activities, such as bicycling and horse riding, butalso to activities related to employment, such as for instance firemenand policemen, which have to protect themselves with adequate reflectormeans when working professionally under conditions with low levels oflighting. In this connection a “reflector means” accomplishes areflection in which light is reflected in directions close to thedirection from which it came.

[0003] In the nowadays existing traffic environment, it is especiallyimportant to protect the head, and this applies to children as well asgrown-ups. However, conventional helmets are not easily noticed, forexample, by motorists at night, and the user may risk injury from atraffic accident on such occasions even if a helmet is used. In order toalert a motorist under these conditions, several types of reflectingwarning signs, which are visible at night, are now commerciallyavailable.

[0004] Ordinary plane reflector means, however, have a limitedprotecting effect by only emitting light when struck by light from onlyone direction. It is true that different kinds of adhesive reflectingtapes exist which can be fastened for example on clothes or helmets.However, a self-adhesive material, such as a sticker, cannot be appliedto a curved surface due to the formation of wrinkles. On the samegrounds, it can neither be applied to a material in the form of a sheetwhich subsequently is fixed onto a curved surface by means ofthermoforming, since the material then will crack or crackle. Due to theabove mentioned problems, reflecting materials according to the state ofthe art rapidly loose their reflecting properties when applied toirregular or curved surfaces.

[0005] The purpose of the invention is thus to provide a reflectingmaterial which can be used both as a reflecting plane sheet per se andas a material for thermoforming, preferably by means of vacuum forming,to a curved or irregular surface, the material retaining its reflectingproperty without crack formation or cracking. In order to achieve thispurpose, the invention has obtained the characterizing features of claim1 and its use has obtained the characterizing features of claim 16.

[0006] In order to explain the invention in more detail, reference ismade to the accompanying drawing, in which

[0007]FIG. 1 schematically shows a cross section through a reflectingmaterial in the form of a sheet according to the invention,

[0008]FIG. 2 schematically shows a cross section through a furtherdevelopment of the embodiment of the material according to theinvention, which is shown in FIG. 1,

[0009]FIG. 3 schematically shows a cross section through an alternativeembodiment of the material according to the invention, and

[0010]FIG. 4 schematically shows a cross section through a materialaccording to a preferred embodiment of the invention.

[0011] In FIG. 1 the material according to the invention is shown in itsmost simple form, and consists of a plane sheet 1 which is coated with areflecting layer 2. The sheet 1 can be of every type of plasticmaterial. However, it is preferred that the sheet comprises atransparent thermoplastic polymer material, preferably crystal-clearpolyvinyl chloride (PVC) or polyester, the polyester being preferredsince it is more harmless to the environment.

[0012] The reflecting layer 2 comprises a suspension of pearls, forexample of glass or plastic, in an adhering substance, preferably alacquer. In this connection a lacquer means a non-pigmented liquid withan organic film forming substance which can be a natural resin, asynthetic resin or an oil. Preferably a so-called screen printinglacquer is used.

[0013] It is an important aspect of the invention that pearls of acertain size are mixed with the adhesive substance. Preferably, thepearls have a diameter between 0.01 and 0.05 mm. The adhesive substancemust be able to attach to the plastic at the same time as it shall beable to bind to the pearls. Thus, the adhering substance comprises anetching transparent glue coating. In this connection etching refers toan increase in surface roughness of the plastic by dissolution of thesame. After the application of the reflecting layer 2, the adheringsubstance in the form of a lacquer is hardened, preferably by means ofheat, but it can also be hardened in other ways, for example by means ofradiation.

[0014] In order to obtain a reflecting laminated material according tothe invention, the adhering substance and pearls of for example glass orplastic are mixed into a suspension which must have a suitableconsistency so that the pearls of microscopic size will be transferredto the plane sheet 1 by means of a known technique in the form of screenprinting (silk screen processing). This is a method which normally isused for applying a pattern to a plastic sheet which is to be subjectedto thermoforming. The size of the pearls is thus also adapted to be ableto pass through the open holes of a screen stencil which normally isused for pressing a pattern medium against the sheet. When the pearlsused are of glass, they must be polished pearls of high quality. Thesame type of glass pearls as in existing reflecting tapes can be usedwith advantage. Preferably, the size of the glass pearls lies within therange of 0.01-0.05 mm.

[0015] By this procedure, the suspension is anchored on the planematerial, a reflecting surface being obtained. The more pearls mixedinto the suspension, the better reflectance is achieved. In thisconnection the amount of glass pearls suspended in the adheringsubstance in the form of a lacquer could surprisingly comprise as muchas 85%. This results in the consumption of 1 kg glass pearls forcovering 4-5 m² of the sheet, which after thermoforming for example canbe used for shells for about 50 helmets of normal size.

[0016] The material according to the invention can in this embodimentalso be used for achieving a reflection in two directions, by thereflective layer being applied to both sides of a suitable surface. Itis of advantage if this surface is a sheet of plastic material which canbe thermoformed. Preferably all kinds of existing materials of polyvinylchloride (PVC) are used, i.e. all thermoplastic materials which comprisepolymers of vinyl chloride. The plane reflecting material can also beused without thermoforming in the form of a traffic sign or anotherwarning sign indicating danger or other circumstances which should beobserved by the public.

[0017] When the reflective layer 2 has been applied to the sheet 1,other patterns can be printed on the material according to theinvention. This is then thermoformed, for example by means of vacuumforming, to a shape corresponding to the curved surfaces, which theshells thus formed are intended to fit. The thermoplastic materialaccording to the invention, in the form of a plane or flexible sheet orfoil of a thickness which is sufficient for vacuum forming, is thenheated to its vacuum forming temperature and formed to a general contourof a mould by means of a pressure difference. Thus, vacuum forming isperformed by means of known techniques at 130° C., the material beingdrawn and stretched to a shell which for example has the shape of ahelmet.

[0018] After cooling, the thin shells formed are sawn into separateunits, and holes are optionally punched out in them. If the shells areto be used in a finished product in the form of a helmet, the shell isfinally glued onto an inner helmet which has a protective effect on thehead.

[0019] The helmet can then, if desired, be built in with a furtherplastic layer. This can be necessary since the virtual reflection can bereduced, i.e. in humid weather. For this reason a further coating isapplied to the finished product, e.g. a layer which protects thereflecting layer and strengthens it even more. As shown in FIG. 2, thiscan be achieved by a further layer 3 of preferably PVC being applied bymeans of for example high-frequency welding to the reflecting layer 2which in turn is disposed on the plane sheet 1.

[0020] A more cost-efficient embodiment of the invention according toFIG. 1 is shown in FIG. 3, a plane sheet 1 of preferably a plasticmaterial being used as above, said material being workable by means ofvacuum forming. In this embodiment a layer 4 a of an adhering substanceis disposed on the sheet 1, and a thin layer 5 of pearls is applied tothe layer 4 a. A further layer 4 b of an adhering substance is againdisposed over this layer 5 of pearls.

[0021] The layers 4 a and 4 b preferably consist of the same transparentglass-clear adhering substance in the form of a lacquer, the lacquer inthe layer 4 a being etching as in the previous embodiment.

[0022] With reference to FIG. 3, the reflecting laminated material isachieved by the etching layer 4 a of adhering substance being applied tothe sheet 1. Pearls are spread onto this layer before it has dried. Thiscan for example be accomplished mechanically with an equipment whichusually is utilised for coating with different kinds of powders. Glasspearls are for example spread in this procedure so that they will falldown onto the still sticky layer 4 a, a monolayer of glass pearlscontacting the same with non-adhering pearls on the top. The sheet withaccompanying layers 4 a and 5 is then allowed to pass an oven for curingof the adhering substance in the layer 4 a. When this layer has beencured, non-adhering glass pearls can be sucked off and reused. Anotherlayer 4 b of adhering substance is then applied to the layer 5 of glasspearls, the sheet with accompanying layers then being allowed to passthe oven again for curing of the layer 4 b.

[0023] The material according to this embodiment of the invention canalso be vacuum formed into a reflecting shell to be applied to a curvedsurface without any crackle formation taken place during the formingprocedure. The reflecting surface is sufficiently well adapted for manyapplications in order to provide for an efficient reflecting effect.

[0024] In FIG. 4 an embodiment is shown which is especially preferredwhen the material according to the invention is to be used forreflecting helmets. By arranging the product in the form of a shell fromthe material according to the invention for example on the inside of abicycle helmet, in which holes have been cut out for the reflectingmaterial, the reflecting product can be used where it is more protectedfrom the surrounding world. In this embodiment this can be achieved by alayer of the material according to the invention being arranged on thatside of the sheet 1 which in the finished helmet will not be directedtowards the light source, i.e. the sheet 1 acts as a protecting layerfor the other layers.

[0025] With reference to FIG. 4, a colour layer 6 is arranged betweenthe sheet 1 and the layer 4 a of an adhering substance. The colour layer6 comprises a transparent dye known in the art, which can be excluded independence of the design and appearance of the final product. Thereflecting layer is arranged as in the preceding embodiment in the formof a single layer of pearls, for example of glass or plastic, betweentwo layers, 4 a and 4 b, of adhering substance. In this connection theadhering substance used should be able to etch dyes as well as plastics.

[0026] A layer 7 of a material with high gloss, for example silver oraluminium, is disposed on the layer 4 b of adhering substance in orderto further amplify the reflection. Preferably, aluminium particles areused. Thus, when the reflecting layer 5 is illuminated, the light notimmediately reflected by this layer will be reflected with totalreflectance by the layer 7 and re-transmitted towards the observer afterreflection by the pearls in the layer 5.

[0027] The layer 7 is preferably applied to the laminate according tothe invention as a paste of commercial aluminium particles by means ofthe above-mentioned technique in the form of screen printing.

[0028] The reflecting laminated material according to the invention canthen be heated to a temperature which is suitable for vacuum forming,e.g. 130° C., vacuum forming then being performed as described above.The reflecting material in the form of a sheet according to theinvention must in this connection have a thickness which is sufficientconsidering the product contemplated after vacuum forming. The materialcan for example be vacuum formed into a shell in the form of a helmetwhich becomes highly reflecting from the outside with the reflectinglayer on the inside of the helmet, the reflecting layer thus beingprotected against all types of damages. In this way a helmet ofimpact-resistant plastic can be achieved with reflecting patterns aswell as usual patterns, which can result in increased road safety,especially for children.

[0029] It should be observed, that a colour layer, if desired, can bearranged in a corresponding way in other embodiments of the invention.In this connection the location of the colour layer in the laminate isnot crucial. A dye can also be mixed into the suspension of pearls andadhering substance, a reflection of the corresponding colour then beingobtained. In this connection the dyes should also be transparent.Furthermore, it is important that all transparent components in thematerial according to the invention retain this property afterthermoforming, such as vacuum forming.

[0030] Warning articles manufactured from the material of the presentinvention present a reflective construction which is durable, rathercheap and quite visible under poor natural light conditions, especiallyat night, when the reflecting articles are illuminated by an externalactive light source, such as a light from a head light of a car. By thevacuum forming property of the inventive material, the invention can beused for increased safety, especially on the roads. Products having anirregular or curved surface can be produced with a functionalreflectance when the present invention is used. Thus, all kinds of lightreflecting products can be achieved, such as bicycle helmets, protectivehelmets for building workers and playing children, and so on.Accordingly, the invention can be used as a reflective device with thecapability of reflecting light and thus being visible from all angles,i.e. a retro-reflecting device generating a reflection in all directionsand usable on a person as such. Other products for increased road safetycan also be obtained by using the invention when a more or lesscompletely reflecting surface is desired, such as hub caps withornaments and reflective patterns.

1. Use of a material comprising a reflecting layer (2, 5) of pearls oftransparent glass or plastic at least partially embedded in an adheringtransparent substance, said layer being arranged at one side thereofadjacent to a first transparent plastic layer (1) comprising polyvinylchloride or polyester, for manufacturing, by means of thermoforming, aretro-reflecting shell which, after cooling, has a curved or irregularsurface shaped as a helmet with the capability of reflecting light inall directions.
 2. Use as in claim 1, characterized in that thethermoforming is vacuum forming.
 3. Use as in claim 1 or 2,characterized in that the material is a plane sheet or a foil.
 4. Use asin claim 1 or 2, characterized in that a second transparent plasticlayer (3) comprising polyvinyl chloride or polyester is arranged on theother side of the layer of pearls, opposite to said first transparentplastic layer (1).
 5. Use as in claim 1 or 2, characterized in that theadhering substance comprises a first and a second layer (4 a, 4 b)surrounding the layer (5) of pearls, the first layer (4 a) beingarranged adjacent to said first transparent plastic layer (1).
 6. Use asin claim 5, characterized in that the pearls in the layer (5) form amonolayer.
 7. Use as in any of claims 1-6, characterized in that thepearls have a diameter between 0.01 and 0.05 mm.
 8. Use as in claim 4,characterized in that when the second plastic layer (3) comprisespolyvinyl chloride it is high-frequency welded to the reflecting layer(2).
 9. Use as in any of claims 1-8, characterized in that the adheringtransparent substance is a lacquer.
 10. Use as in claim 9, characterizedin that the lacquer is a screen printing lacquer.
 11. Use as in any ofclaims 1-5, characterized in that a layer (6) of a transparent dye isarranged adjacent to said first transparent plastic layer (1).
 12. Useas in claim 5, characterized in that a high gloss material layer (7) isarranged adjacent to said second layer (4 b) of the adhering substanceopposite to the reflecting layer (5) of pearls.
 13. Use as in claim 12,characterized in that the high gloss material layer (7) comprisesaluminium particles.